Plant Protection Science – 2002
Control of Ergot (Claviceps purpurea (Fr.) Tul.) Ascoscarpus Formation under the Impact of Chemical and Biological Seed Dressing
Z. DABKEVIČIUS* and R. SEMAŠKIENĖ
Department of Plant Protection, Lithuanian Institute of Agriculture, LT 5051 Kėdainiai, Lithuania
*E-mail: [email protected]
Abstract
The present paper discuses the feasibility of ergot contaminants control in rye seeds through seed dressing. The objec- tive of the work was to determinate the impact of chemical and biological seed dressing on sclerotia germination and ascocarps formation. Germination (%) of sclerotia treated with most of the investigated fungicidal action chemical seed dressers was significantly lower than that of untreated sclerotia. Although some chemical seed dressers did not give very good control of sclerotia germination, they delayed ascocarps emergence and significantly reduced their number above the soil surface at rye anthesis. Biocontrol agents did not have any significant effect on sclerotia germination and ascocarps formation.
Keywords: Claviceps purpurea; ergot; sclerotia; ascocarps; winter rye; chemical and biological seed dressers
INTRODUCTION 1986). But many new seed dressers are not currently approved for application as treatment to control ergot. Ergot, Claviceps purpurea (Fr.) Tul., occurs to some This study was conducted to investigated the feasibil- extent on Poacea family plants in Lithuania every year. ity of ergot contaminants control in rye seeds by seed 79 wild and cultivated plant species and forms were dressing. The objective of the work reported in this identified to be affected by ergot. The disease was paper is to determinate the impact of chemical and found in 5 cereal species (DABKEVIČIUS 1997). Ergot biological seed dressing on sclerotia germination and is generally more prevalent in rye and triticale than in ascocarps formation. the other cereals. During 1996–2000 65.9% of winter rye stands and 40.3% of winter triticale stands of the MATERIALS AND METHODS total area under observation were affected by ergot. On average 4.0 and 4.7% of ears were with sclerotia Sclerotia of C. purpurea were collected from winter in the affected area (DABKEVIČIUS & SEMAŠKIENĖ rye fields in Dotnuva, Kėdainiai District. 300 sclero- 2001). In nature the sclerotia of C. purpurea mature at tia were mixed with rye seeds up to 1 kg to provide about the same time as the healthy grain. At harvest, sufficient bulk for application of seed dressers in a some sclerotia fall to the ground but many are col- Hege 11 at manufactures’ recommended rates. Ten lected with the seed (LOVELESS & PEACH 1986). Small chemical seed dressers with different mode of action sclerotia and their pieces similar in size and shape to and composition as well as two biocontrol agents based cereal seeds may pass through cleaning machinery, on micro-organisms’ antagonistic action were used in and eventually be sown alongside with seed. One the experiment. The following chemical seed dressers way to decrease the risk of infection is seed dressing. were tested: triadimenol 15 g/kg + fuberidazol 2.0 g/ Some authors have investigated the influence of some kg + imazalil 2.5 g/kg (trade name Baytan Universal seed dressers on sclerotia germination (SHAW 1984, 19.5 WS, rate 2.0 g/kg seeds), flutriafol 25 g/l +
Proc. 6th Conf. EFPP 2002, Prague. Plant Protect. Sci., 38 (Special Issue 2), 2002: 681–683 681 Vol. 38, Special Issue 2: 681–683 Plant Protection Science – 2002 Plant Protection Science – 2002 Vol. 38, Special Issue 2: 681–683 tiabendazol 25 g/l (Vincit 5 SC, 2 ml/kg), carboxine For the statistical analysis, the data were arc sine 200 g/l + thiram 200 g/l (Vitavax 200 FF, 3.0 ml/kg), transformed to stabilise the variance. The significance of guazotine 350 g/l (Panoctine 35 LS, 2.0 ml/kg), fludi- data was determined by F test with a significance level oxonil 25 g/l (Maxim 025 FS, 2.0 ml/kg), fludioxonil of P ≤ 0.01 and P ≤ 0.05. 25 g/l + epoxiconazole 10 g/l (Maxim Star 035 FS, 1.5 ml/kg), tebuconazole 20 g/kg (Raxil 2WS, 1.5 g per RESULTS AND DISCUSSION kg), ethirimol 40 g/l + utriafol 1 g/l + thiabendazole 3 g/l (Ferrax, 3 ml/kg), benomyl 500 g/kg (Funda- In field experiments sclerotia germination was de- zol 50WP 2.5 g/kg), carboxine 750 g/kg + imazalil fined as the presence of at least one ascocarp, visible 25 g/kg (Kemikar 775 WP, 2 g/kg). Fungus Tri- on the soil surface. In both experimental years the choderma lignorum strain istokskij (titre 109spor/g) first ascocarps were identified on the soil surface at and bacteria Pseudomonas aureofaciens (trade name rye heading. Untreated and treaded with biocontrol Kaelsi-Micros, rate 0.2 ml/kg seeds) were used as agents sclerotia start to germinate at the same time biocontrol agents. The counted sclerotia were subse- and at the same intensity. 23.0% of untreated and quently separated from the rye grain/sclerotia mixture. treated with bacteria Pseudomonas aureofaciens sclerotia Treated and untreated ergot sclerotia were placed on germinated at winter rye GS 55-59. After application 1 m long rows in late October in the unsown patch on with fungus Trichoderma lignorum 19.5% of sclerotia rye fields. The rows were arranged in a completely germinated. In both years sclerotia germination and randomized design with five replicates. 20 sclerotia ascocarpus formation in untreated and treated rows per row under field were inserted in the soil at depth was the most intensive at winter rye GS 61-65. After of 2 cm. The assessments of germinated sclerotia GS 69 ascocarps start decline. In this paper we have and ascocarp production were begun at the beginning presented results of the efficacy of seed dressers with of winter rye heading and were finished at end of different mode action at GS 69, when the maximum anthesis. The number of ascocarps visible above the of germinated sclerotia was determined. Germination soil surface were determined during each assessment of untreated sclerotia was on average 49% (Figure 1). (every 4 days). The experiments were continued for Most decreases in sclerotia germination after chemi- two years.
60 49 50 42NS 37NS Significantly different from untreated 40 32* 32* 33NS *P ≤ 0.05, **P ≤ 0.01. NS – not 30 22** significant at P ≤ 0.05 g 19** 20 13** 9** 10 2** 4** 2**
Mean germination (%) Figure 1. Effect of seed treatments 0 1 2 3 4 5 6 7 8 9 10 11 12 13 on sclerotia germination (%)
450 387NS 400 360 Significantly different from untreated 350 303NS 300 **P ≤ 0.01. NS – not significant 231** 250 P ≤ 0.05 180**196** 200 128** 150 98** 100 66** 55** Figure 2. Effect of seed treatments 11** 15** 50 7** on the number of ascocarps emer- 1 2 3 4 5 6 7 8 9 10 11 12 13 Number of emerged ascocarps 0 ging above the soil surface Explanation for Figures 1 and 2: 1 – Untreated 6 – Fludioxonil 10 – Benomyl 2 – Fuberidozole/imazalil/triademinol 7 – Fludioxonil/epoxiconazole 11 – Carboxin/imazalil 3 – Flutriafol/tiabendazole 8 – Tebeconazole 12 – T. lignorum 4 – Carboxin/thiram 9 – Ethirimol/utriafol/thiabendazole 13 – P. aureofacienns 5 – Guazatine
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cal seed dressing were satisfactory and significant. not give very good control of sclerotia germination, Guazatine, benomyl and fludioxonil reduced fungal they delayed ascocarps emergence and significantly growth very well. Only 2–4% of sclerotia germinated reduced their number above the soil surface at rye after application of these compounds. A similar efficacy anthesis. Biocontrol agents did not have any signifi- of guazatine and fludioxonil on sclerotia germina- cant effect on sclerotia germination and ascocarps tion was obtained in Belarus (BUGA & NEMKOVICH formation. 1997). Fludioxonil/epoxiconazole, ethirimol/flutraifol/ thiabendazole, carboxin/imazalil and carboxin/thiram References gave a good decrease of sclerotia germination with high level of significance (P ≤ 0.01). Fuberidazole/ BUGA S.F., NEMKOVICH A. I. (1997): Effect of seed dress- imazalil/triadimenol and flutriafol/tiabendazole showed ing on the germination of spore sclerotia of Claviceps the lowest significant effect on sclerotia germination. purpurea (Fr.) Tul. Vestsi Akademii Agrarnykh Nauk Efficacy of biocontrol agents and tebuconazole was Respubliki Belarus, No. 4: 56–58. low and not significant. DABKEVIČIUS Z. (1997): Investigations of Claviceps Untreated germinated sclerotia formed 360 ascocarps purpurea (Fr.) Tul. In the Poacea family plants in Li- (Figure 2). All chemical seed dressers with fungicidal thuania. In: DEHNE H.-W. et al. (ed.): Diagnosis and action significantly decreased ascocarps emergence. Identification of Plant Pathogens. Netherlands, Kluwer Only P. aureofaciens and T. lignorum did not have Acad. Publ.: 299–301. any effect on ascocarps formation. Most of the tested DABKEVIČIUS Z., SEMAŠKIENĖ R. (2001): Occurrence and chemical seed dressers reduced emerged the number of harmfulness of ergot (Claviceps purpurea (Fr.) Tul.) in ascocarps per 1 germinated sclerotia. After application cereals crops of Lithuania. Biologija (Biology). No. 3: of fludioxonil and benomyl the number of ascocarps 8–10. per 1 germinated sclerotia decreased 49.3 and 52.0%, LOVELESS A.R., PEACH J.M. (1986): Evidence from respectively. Fludioxonil/epoxiconazole, tebuconazole ascospores from host restriction in Claviceps purpurea. and biocontrol agents did not have any effect on the Transaction British Mycology Society, 86: 603–610. number of ascocarps on germinated sclerotia. Other SHAW S. (1984): Evaluation of triadimenol and other chemical dressers reduced ascocarps emergence on chemical seed treatments for the control of ergot (Cla- sclerotia 16.4–42.5%. viceps purpurea) in contaminated seed. In: British Crop Generally, germination (%) of sclerotia treated with Protection Conf. Pest and Diseases. BCPC, Farnham: most of the tested fungicidal action chemical seed 53–58. dressers was significantly lower than that of untreated SHAW S. (1986): Evaluation of Baytan for control of ergot sclerotia. Although some chemical seed dressers did contaminants in cereal seed. Panzenschutz-Nachrichten Bayer, 39: 47–70.
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